PRESENTED BY GROUP 7 PCL2

Rotavirus

GROUP 7 MEMBERS: NSABIMANA Venuste 12113664NYAZIYOSE Ignace 12113538 NZABONIMPA Clarisse 12112932 NZIYOMAZE Elie 12114015 NZAHUMUNYURWA Donat 12113484 RUGIRA Vive 12113869 RUKAMBA Jean de Dieu 12113905 SHABELI Philippe 12113979 SHEMA Origène 12114300 SIMBI Credo Sylvie 12113714 TSEMO Tagne Sandrine 213003054 TUYISENGE Elius 12113225 

ROTAVIRUSROTAVIRUSFamily Reoviridae

Genus Rotavirus

INTRODUCTION

Diarrheal disease has been recognized in humans since antiquity.

Until the early 1970s, a bacterial, viral, or parasitic etiology of diarrheal disease in children could be detected in fewer than 30% of cases

In 1973, Bishop and colleagues observed a virus particle in the intestinal tissue of children with diarrhea by using electron micrography.

This virus was subsequently called “rotavirus” because of its similarity in appearance to a wheel (rota is Latin for wheel).

INTRODUCTION

First isolated in 1973 from children with

diarrhea

EM identification from duodenal biopsies

Human and animal strains are anti-genetically

distinct, and animal strains rarely cause

infection in humans.

INTRODUCTION CONT’

60-80nm in size

Non-enveloped virus Double capsid virus EM appearance of a wheel with

radiating spokes Icosahedral symmetry double stranded (ds) RNA in 11

segments

CLASSIFICATION

Groups, subgroups,

serotypes based on viral capsid proteins :

7 Groups (A through G)

Group A is the most common and has 2

subgroups

10 human serotypes based on G protein (VP 7)

Classification of rotaviruses is grouped into

serogroups and then serotypes , 7 antigenetically

different

sero-groups – A-G

Group A rotaviruses • Cause most human disease – Further subdivided into subgroups • Principal etiologic agent of severe gastroenteritis in infants and young children • Responsible for 1 billion cases of severe diarrhea • Major cause of mortality among the young

GROUP A ROTAVIRUSES Cause most human disease Further subdivided into subgroups • Principal etiologic agent of severe

gastroenteritis in infants and young children

• Responsible for 1 billion cases of severe diarrhea

Major cause of mortality among the young

OTHER ROTAVIRUSES • Group B – Adult diarrhea

• Group C – Primarily veterinary pathogens

• Groups D, E, F, G – Only known to infect animals

EPIDEMIOLOGY - WORLDWIDE

Millions are affected

600,000-850,000 deaths/year

A major cause of diarrhea-associated

hospitalizations

Seroprevalence studies show that

antibody is present in most by age 3.

ROTAVIRUS-WORLDWIDE DISTRIBUTION

Estimated Global Distribution of The 800,000 Annual Deaths

Caused By Rotavirus Diarrhea

. prevalent

area

EPIDEMIOLOGY : U.S

No. of children under 5y. affected ~ 2.7

million

Physician visits per year ~ 500,000

Hospitalizations per year ~ 50,000

Deaths per year ~ 20 - 40

% cases w/ dehydration ~ 1-2.5%

EPIDEMIOLOGY

Age- 4months - 2 years

Protection of younger infants through

transplacental antibody transfer

Asymptomatic infections are common,

especially in adults

Nosocomial infections

Outbreaks

EPIDEMIOLOGY

Seasonality

Winter months (Nov. through May in US)

Gradual spread W to E

Year-round in the tropics

Incubation period - thought to be <4 days

EPIDEMIOLOGYDIFFERENCES IN GROUPS

Group A infections are most common in human

Group B has been associated with outbreaks in adults in China

Group C is responsible for sporadic cases of diarrhea in infants around the world

PATHOGENESIS

Targeted host cells- mature enterocytes

lining the tips of intestinal villi

Intermediate/infective sub-viral particle

(ISVP) produced through proteolysis

enter host cell by endocytosis

ROTAVIRUS- EM STRUCTURE

ROTAVIRUS- 3D STRUCTURE

VIRAL STRUCTURAL PROTEINS (VP)

Outer structural proteins - VP7 and VP4

VP7VP7=glycoprotein

VP4VP4=protease-cleaved, P protein, viral

hemagglutinin, and forms spikes from the

surface

Inner core structural proteins VP 2, 3, 6

VP6 is an important antigenic determinant

VP4 determines how virulent the virus is

and it determines the P-type of the virus.

Genome is composed of 11 segments of double-

stranded RNA coding for six structural and five

nonstructural

proteins

Seven serological groups have been identified (A-G), three of which (groups A, B, and C) infect humans .

NONSTRUCTURAL VIRAL PROTEINS

NSP1, the product of gene 5, is a nonstructural RNA-binding protein.

NSP2 is an RNA-binding protein that accumulates in cytoplasmic inclusions (viroplasms) and is required for genome replication.

NSP3 is bound to viral mRNAs in infected cells and it is responsible for the shutdown of cellular protein synthesis.

NON STRUCTURE PROTEINS NSP4 is a viral enterotoxin to induce

diarrhoea and was the first viral enterotoxin discovered.

NSP5 is encoded by genome segment 11 of rotavirus A and in virus-infected cells NSP5 accumulates in the viroplasm.

NSP6 is a nucleic acid binding protein, and is encoded by gene 11 from an out of phase open reading frame.

ROTAVIRUS STRUCTURE

Gene coding assignment

ROTAVIRUS - PROPERTIES

Virus is stable in the environment

Relatively resistant to hand washing agents

Susceptible to disinfection with 95% ethanol,

‘Lysol’, formalin

REPLICATION There are two possible ways of entry in

the cell: Direct penetration of the virion across the

plasma membrane Endocytosis

EARLY EVENTS

Early transcription, translation, and assembly of double-layered particles.

Some of the (+) RNA that is synthesized functions as mRNA . NSP2 and NSP5 play roles in the assembly of viroplasms, where cores are assembled from VP1, VP2 and VP3.

Some of the (+) RNA functions as templates for synthesis of (−) RNA.

VP6 is added to the core to form a progeny double-layered particle.

LATE EVENTS

Late transcription, translation and virion assembly.

NSP4 is synthesized in the endoplasmic reticulum,where it binds VP4 and a double-layered particle .

This complex buds into the endoplasmic reticulum, where the final stages of assembly occur.

VP7, also synthesized in the endoplasmic reticulum, is added to form the outer

layer of the capsid and the VP4 spikes are added. Virions are released from the cell either by lysis or by

exocytosis

CLINICAL FEATURES

Incubation period - thought to be <4 days

Fever- can be high grade (>102F in 30%)

Vomiting, nausea precede diarrhea Diarrhea

- usually watery (no blood or leukocytes)

- lasts 3-9 days

- longer in malnourished and immune deficient indiv.

- NEC and hemorrhagic GE seen in neonates

HISTOPATHOLOGY

Mature enterocytes lining the tips of intestinal villi

are affected

Villous atrophy and blunting

Death of the mature enterocytes

HISTOPATHOLOGY

MECHANISM OF DIARRHEA Watery diarrhea due to net secretion of

intestinal fluid

Activation of the enteric nervous system -possible role of enterotoxin

CLINICAL FEATURES (CONTD.)(CONTD.)

Dehydration is the main contributor to mortality.

Secondary malabsorption of lactose and fat, and chronic diarrhea are possible

CONT’• Recovery is usually complete.

• However, severe diarrhea without fluid and electrolyte

replacement may result in dehydration and death .

Immunological Aspects

• Immunoglobulin (Ig A) , in the lumen of the gut immunity

to infection .• Actively or passively acquired antibodies (including antibodies

in

colostrum and mothers milk) lessen the severity of disease

but does not consistently prevent reinfection .• Absence of antibody small amounts of virus infection

and diarrhea .

DIAGNOSIS

Antigen detection in stool by ELISA, Latex

Agglutination (for Group A rotavirus)

EM- non-Group A viruses also

Culture- Group A rotaviruses can be

cultured in monkey kidney cells

Serology for epidemiologic studies

TRANSMISSION Mainly person to person via fecal-oral route

Fomites

Food and water-borne spread is possible

Spread via respiratory route is speculated

TREATMENT AND PREVENTION

Treatment Supportive - oral, IV rehydration

PreventionHand washing and disinfection of surfaces

ROTAVIRUS VACCINE• Rotarix which is the latest(licensed in 2008) RotaTeq(Rhesus rotavirus tetravalent vaccine) licensed

in 2006

– Serotypes 1, 2, 3, 4 for VP7

– Reassortant strains

– Protective against 80% of the cases of severe diarrhea, 100% of the dehydration cases

Rotashield

• Was recommended at 2, 4 and 6 months of age

• Risk of intussusception (a bowel blockage that is treated in a hospital and may require surgery) 1 in 12,274 infants

REFERENCES

Links: www.ncbi.nih.gov/pmc www.diarrhea.emedtv.com/rotavirus www.bvgh.org/biopharmaceutical www.pubmed.com www.cdc.comBook: Lange microbiology and Immunology review

(10th Edition)

THANK YOU FOR YOUR KIND ATTENTION !!!